A distributed antenna system (“DAS”) can provide a signal transport network for communicating signals between one or more base stations and mobile communication devices or other terminal devices. The DAS may include master units and remote antenna units. The master units may be connected to the base stations. The master units receive downlink signals from the base stations and distribute downlink signals in analog or digital format to multiple remote antenna units. The remote antenna units transmit downlink signals to mobile communication devices or other terminal devices within coverage areas serviced by the remote antenna units. In the uplink direction, the remote antenna units receive uplink signals from terminal devices in the serviced coverage areas. The remote antenna units may combine uplink signals and transmit the combined uplink signals to master units. The master units may transmit uplink signals to the serving base stations.
A signal transport network provided by a DAS may be implemented using analog systems or digital systems. A digital system can include one or more devices for digitizing analog downlink signals received from a base station. A digital representation of the analog waveform is used to transmit the downlink signal via the DAS.
A master unit may route an entire downlink signal to remote antenna units of the DAS. Routing an entire downlink signal to remote antenna units can involve unnecessarily routing frequency bands in which no voice data or other data is transmitted.
It is desirable to distinguish sub-bands of signals communicated via a DAS that include voice or other data from sub-bands in which no voice data or other data is transmitted.